Activate_Virtual_Screen


Purpose   Redirects all subsequent screen writing activity to a virtual
          screen.

Decln.    Activate_Virtual_Screen(Page:byte);

Remarks   Page is the number of the virtual screen to activate. It must be
          in the range 1 to Max_Screens and must have been created with
          CreateScreen or SaveScreen.

Example

BEGIN
    CREATESCREEN(3,25);
    ACTIVATE_VIRTUAL_SCREEN(3);
    CLEARTEXT(1,1,80,25,WHITE,BLUE);
    WRITECENTER(1,YELLOW,BLUE,'HELP SYSTEM');
    ......
    SLIDERESTORESCREEN(3,DOWN);
    ACTIVATE_VISIBLE_SCREEN;
END;

Virtual screen number 3 is created and all screen writes are redirected to
it with the Activate_Virtual_Screen procedure. The virtual screen is
displayed to the user by sliding it down onto the display.